1. Field of the Invention
The present general inventive concept relates to an apparatus and method of fabricating a color filter, and more particularly, to an apparatus and method of fabricating a color filter using an ink-jet technique.
2. Description of the Related Art
Recently, flat display devices, such as a liquid crystal display (LCD), a plasma display panel (PDP), an organic electro luminescence (EL) displays (expand exactly), a light emitting diode (LED), and a field emission display (FED), are being used to increase the size of a screen so as to display information from a TV and a computer. From among these flat display devices, LCDs are mainly used for a computer monitor and a notebook PC or the like due to low power consumption.
A color filter, which forms an image of a desired color by passing white light modulated by a liquid crystal layer, is disposed on an LCD. The color filter has a structure in which a plurality of red (R), green (G), and blue (B) pixels are arranged on a transparent substrate to have a predetermined shape. Methods of fabricating a color filter include a dyeing method, a pigment dispersion method, a printing method, and electrodeposition method or the like.
However, in the methods of fabricating a color filter as listed-above, a predetermined process must be repeatedly performed according to each color so as to form red (R), green (G), and blue (B) pixels, and thus, a process efficiency is lowered and fabrication costs increase.
Thus, a method of fabricating a color filter using an ink-jet technique by which a fabrication process is simplified and fabrication costs are reduced has been proposed. In such method of fabricating a color filter using an ink-jet technique, ink droplets of predetermined colors such as red (R), green (G), and blue (B) are ejected into each pixel region of a substrate through nozzles of an ink-jet head, and thereby, forming a pixel of a predetermined color.
FIG. 1 illustrates an example of a method of fabricating a color filter by ejecting ink into each pixel of a color filter 10 using an ink-jet head 20, FIG. 2 illustrates the color filter 10 fabricated by the method of FIG. 1 that is divided into regions according to ink thickness, FIG. 3 is a graph illustrating an ink thickness taken along line I-I′ of FIG. 2, and FIG. 4 is a graph illustrating an ink thickness taken along line II-II′ of FIG. 2.
Referring to FIG. 1, the ink-jet head 20 comprising first through fourth nozzles 21, 22, 23, and 24 ejects ink into each pixel 11 by passing an upper portion of the color filter 10 in a certain direction (Y-direction) while the ink-jet head 20 is inclined at a predetermined angle with respect to the color filter 10. The ink-jet head 20 moves in an X-direction and then moves in a Y-direction while ejecting ink into each pixel 11. By repeatedly performing such a process, all of the pixels 11 of the color filter 10 are filled with ink.
However, as the ink-jet head 20 moves while the ink-jet head 20 is inclined at a predetermined angle with respect to the color filter 10, a difference in the amount of ink ejected through the first through fourth nozzles 21, 22, 23, and 24 occurs according to the number of nozzles for ejecting ink in a predetermined region in which the ink-jet head 20 passes over and leaves the color filter 10.
Referring to FIGS. 2 and 3, the amount of ink ejected through the first nozzle 21 decreases in region 1 along the Y-direction and a predetermined amount of ink is ejected in region 2 along the Y-direction. However, ink ejected through the fourth nozzle 24 is ejected in region 2 to a predetermined thickness along the Y-direction and the amount of ink gradually increases in region 3 along the Y-direction.
This is because the number of nozzles passing each region (regions 1, 2, and 3) is different as the ink-jet head 20 moves in the Y-direction. In detail, in region 2, all of the first through fourth nozzles 21, 22, 23, and 24 operate and ink is ejected through the first through fourth nozzles 21, 22, 23, and 24. However, in region 1, the number of nozzles for ejecting ink gradually increases as the first nozzle 21 to the third nozzle 23 sequentially enter region 1 of the color filter 10 and in region 3, the number of nozzles for ejecting ink gradually decreases as the third nozzle 23 to the first nozzle 21 sequentially leave region 3 of the color filter 10. Thus, the amount of ink ejected in region 1 and region 3 can be larger than the amount of ink ejected in region 2.
Referring to FIGS. 2 and 4, a fin 13 in which an ink thickness rapidly increases is formed at a boundary 12 of the ink-jet head 20 along the X-direction. This is because the ink thickness of the boundary 12 can be increased when a working section of the ink-jet head 20 varies along the X-direction.
Hence, since cross-talk between an operating nozzle and a non-operating nozzle from among the first through fourth nozzles 21, 22, 23, and 24 occurs, a difference in the amount of ink ejected may occur according to the number of other simultaneously-operating adjacent nozzles. However, the reverse case may occur.
In this way, due to interference between the operating and non-operating nozzles, a difference in the amount of ink ejected through one of the first through fourth nozzles 21, 22, 23, and 24 may cause a difference in an ink thickness of a pixel and due to the non-uniformity of ink thickness in a partial region of the color filter 10, the reliability of color reproduction can be lowered and a perception of color by a viewer can be reduced.